1. Field of the Invention
The present invention relates to a stereoscopic image capture device for inputting a stereoscopic image to be displayed by a three-dimensional image display device.
2. Description of the Related Art
A three-dimensional image display device, which allows an observer to perceive the stereoscopic image by reproducing the intensity and direction of a light beam recorded by an image capture device, is conventionally known. Hereinafter, this reproduction method is referred to as a light reproduction method. The principle of recording and reproduction of the stereoscopic image by employing the light reproduction method will be briefly described below.
First, as shown in FIG. 10, an image of an object is recorded while a slit array 32 is placed in front of a recording face 31. As in a CCD, the recording face 31 is pixellated and each pixel of the recording face 31 records a respective section of the image of an object to be recorded. Although light beams are diffused in every direction from each of objects A and B, only the light beams passing through slits of the slit array 32 can reach the recording face 31. Therefore, the position of each slit corresponds to the position of a microcamera. If only the horizontal components of the light carrying the image are considered, only a light beam incident on the pixel of the recording face 31 at an angle determined by the positional relationship between the pixel and a corresponding slit is recorded in the pixel of the recording face 31. Regarding the vertical components, it is necessary to converge the vertical components of the light on the recording face 31 through a lens. However, the description thereof is herein omitted since it is not relevant to the principle of the present invention.
The thus recorded image is reproduced by a three-dimensional display device having such a configuration that a slit array 34 is disposed in front of a pixellated display face 33 as shown in FIG. 11. In order to prevent the fore part and the back part of the reproduced image from being inverted in a depth direction, the pixel order within each group of pixel is inverted (i.e., the image section recorded as the left-most pixel of a slit becomes as that slit's right-most pixel). The light beam going out from one pixel to pass through a slit travels only in the direction determined by the positional relationship between the pixel and the corresponding slit. Since a recording pixel and a corresponding display pixel are symmetrically positioned relative to the slit, the light beams passing through the slit array panel 34 travel in the same directions as those during recording. An observer can perceive the stereoscopic image by observing the thus travelling light beam. More specifically, the light beams actually travel in a forward direction (that is, in a direction toward an observer) from the display face 33. Since information of one object point travels from a plurality of pixels (for example, pixels a5, b3 and c2) via a plurality of corresponding slits (a, b and c) at different angles, the observer perceives as if the light beams travel from one object point located far behind the display face 33. Since such a phenomenon occurs for all display points, the observer can perceive a stereoscopic view.
Although the slit array is used in the above conventional three-dimensional display device, a cylindrical lens array (i.e., a lenticular lens) can be used instead in the light reproduction method since the cylindrical lens array has an equivalent function as that of the slit array.
FIG. 12 shows an example of an image capture device employing the light reproduction method. This image capture device includes: an image capturing face 101; a cylindrical lens array 102 disposed in front of the image capturing face 101; and a cylindrical lens 103 for converging vertical components, disposed in front of the cylindrical lens array 102. Since the cylindrical lens 103 has a curvature only in the vertical direction, it does not affect the horizontal components.
The image capturing face 101 is disposed on a focal plane of the cylindrical lens array 102. The horizontal components of light beams are recorded by the cylindrical lens array 102 at the positions on the image capturing face 101 determined by the incident angles of the light beams. Since each cylindrical lens of the cylindrical lens array 102 functions as a microcamera, it is considered that the image capture device shown in FIG. 12 includes a plurality of cameras, e.g., several tens to several hundreds of cameras arranged in a parallel manner. In the example shown in FIG. 12, the image capturing face 101 should have the same size as that of the display face of the three-dimensional display device. Moreover, a pixel pitch of the image capturing face 101 should be the same as that of the display panel serving as the display face of the three-dimensional display device.
Another example of an image capture device used in the light reproduction method is disclosed in Japanese Laid-Open Patent Publication No. 1-254092. FIG. 13A is a horizontal cross-sectional view showing an image capture device disclosed in the aforementioned Patent Publication, and FIG. 13B is a vertical cross-sectional view of a pinhole plate 106 shown in FIG. 13A. The image capture device includes: an image capturing face 104; a convex lens 105 disposed in front of the image capturing face 104; and the pinhole plate 106 disposed onto the front face of the convex lens 105. A distance between the image capturing face 104 and the convex lens 105 is set so as to be equal to a focal length f of the convex lens 105. An electric optical device such as a liquid crystal device is used as the pinhole plate 106. A pinhole 107 is movable on the pinhole plate 106. Japanese Laid-Open Patent Publication No. 1-254092 also shows a Fresnel lens as the convex lens 105. For better understanding of the present invention, however, FIGS. 13A and 13B show a conventional planoconvex lens having the same function.
In the image capture device having the configuration as shown in FIGS. 13A and 13B, the position of the movable pinhole 107 corresponds to the position of a general viewing point of a camera. Therefore, a plurality of images taken at a plurality of viewing points of the camera are imaged on the image capturing face 104 in a time divided manner. Thus, the position of the pinhole 107 corresponds to one cylindrical lens of the cylindrical lens array 102 shown in FIG. 12. Similar to the example shown in FIG. 12, the image capturing face 104 and the display face of the three-dimensional display device should also be equal to each other in size in this conventional example. However, by scanning in a time divided manner, one image corresponding to the image on the entire image capturing face 104 shown in FIG. 12 can be obtained. Therefore, the size of one image can be reduced, resulting in reduction in size of the image capturing face 104.
However, the aforementioned conventional techniques have the following problems.
In the image capture device shown in FIG. 12, the image capturing face 101 is required to be equal in size to the display face as described above. Moreover, the pixel pitch of the image capturing face is required to be equal to that of the display face. However, it is extremely difficult to constitute such an image capturing face by a photoelectric conversion device such as a CCD, that is, it is next to impossible to realize such an image capturing face.
On the other hand, in the image capturing device shown in FIGS. 13A and 13B, the position of the pinhole 107 is required to be moved at high speed, e.g., the pinhole is required to scan the image 60 times per second, in order to prevent the flicker of the image. However, a device suitable for constituting an optical shutter capable of responding at such a high speed does not exist at present. When it is assumed that 500 images are taken by one scanning and the scanning is performed at a rate of 60 times per second, it is necessary to take 30000 frames of the image per second. However, such an image capture device operating at high speed does not exist. Moreover, in the case where the image is scanned at such a slow rate that the device can follow, a motion picture cannot be taken.